Identification
A:
It complies with the test for Fatty acid composition.
B:
It complies with the test for Melting range.
Acid value 401
Dissolve about 10 g of Hydrogenated Cottonseed Oil, accurately weighed, in 50 mL of a hot mixture of neutralized alcohol and toluene (1:1), add 0.5 mL of phenolphthalein TS, and titrate with 0.1 N potassium hydroxide VS to produce a permanent, faint pink color: the acid value so obtained is not more than 0.5.
Alkaline impurities
Dissolve by gentle heating 2.0 g of Hydrogenated Cottonseed Oil in a mixture of 1.5 mL of alcohol and 3.0 mL of toluene. Add 0.05 mL of
bromophenol blue TS, and titrate with 0.01 N hydrochloric acid to a yellow endpoint: not more than 0.4 mL of 0.01 N hydrochloric acid is required.
Limit of nickel
Test solution
Weigh 5.0 g of Hydrogenated Cottonseed Oil into a previously tared platinum or silica crucible. Cautiously heat and introduce into the substance a wick formed from twisted ashless filter paper. Ignite the wick. When the substance ignites, stop heating. After combustion, ignite in a muffle furnace at about 600
. Continue the incineration until white ash is obtained. After cooling, transfer the residue, with the aid of two 2-mL portions of diluted hydrochloric acid, to a 25-mL volumetric flask, add 0.3 mL of nitric acid, and dilute with water to volume.
Nickel standard solution
Immediately before use, dilute 10 mL of nickel standard solution TS with water to 500 mL. This solution contains the equivalent of 0.2 µg of nickel per g.
Standard solutions
Into three identical 10-mL volumetric flasks, introduce respectively 1.0, 2.0, and 4.0 mL of Nickel standard solution. To each flask, add a 2.0-mL portion of the Test solution, and dilute with water to volume.
Procedure
Concomitantly determine the absorbances of the
Standard solutions and the
Test solution at least three times each, at the wavelength of maximum absorbance at 232.0 nm, with a suitable atomic absorption spectrophotometer (see
Spectrophotometry and Light-Scattering 851) equipped with a graphite furnace and a nickel hollow-cathode lamp. Record the average of the steady readings for each of the
Standard solutions and the
Test solution. Plot the absorbances of the
Standard solutions and the
Test solution versus the added quantity of nickel. Extrapolate the line joining the points on the graph until it meets the concentration axis. The distance between this point and the intersection of the axes represents the concentration of nickel in the
Test solution. Not more than 1 µg per g is found.